1. Field of the Invention
The present invention relates to a process of calibrating a blood sugar analyzing apparatus having a fixed glucose oxidase membrane (also known as fixed enzyme membrane).
2. Description of the Prior Art
A blood sugar analyzing apparatus of the type described above measures the blood sugar content or glucose concentration in a blood specimen which can be, for example, total blood, blood serum or plasma of a human or animal or of a standard solution (hereinafter collectively referred to as blood specimen or the like). The apparatus supplies a glucose containing specimen to the enzyme membrane sensor in order to generate a reaction current which is proportional to the blood sugar concent.
The blood sugar analysing apparatus comprises a fixed enzyme membrane electrode for measuring the reaction current (a reduction current which flows when reducing hydrogen peroxide generated upon decomposition of the glucose by the fixed enzyme membrane), a reaction cell housing the fixed enzyme membrane electrode and the blood specimen or the like, and a liquid pump for drawing a buffer liquid for washing the reaction cell.
The blood sugar analyzing apparatus is used for clinical tests with respect to diabetes, and should preferably provide a linear relationship between actual blood sugar concentrations in blood specimens and measured blood sugar concentrations. However, in the past such a linear relationship was not possible, since beyond a certain blood sugar concentration, analyzed values are lower than actual blood sugar concentrations. No satisfactory measures have heretofore been found to correct this problem. There has been a need for a blood sugar analyzing apparatus which has good linearity between measured and actual blood sugar concentrations.
With conventional measurement processes, a complex manual adjustment operation is required in order to determine a calibration coefficient using a standard solution. There is a tendency for such a calibration coefficient to be incorrectly determined when the amounts of the samples analyzed differ since only one calibration operation is normally performed. This results in a failure to maintain a required degree of accuracy in the blood sugar measurements.